The present invention relates to a new and improved method of measuring fluid pressure i.e. liquid or gas pressure in a sealed bore hole. The present invention also relates to a new and improved construction of a measuring tube for measuring such pressure as well as to a new and improved construction of a measuring probe for such measuring tube.
In its more particular aspects, the present invention specifically relates to a new and improved method for measuring fluid pressure in a sealed bore hole by means of a measuring tube inserted into the bore hole. In given areas or regions of the bore hole where the pressure measurement is to take place and on both sides of each area or region in which the respective measurement is planned, the bore hole is sealed by sealing means which are provided between the bore hole wall and the outer wall of the measuring tube. The measurement takes place by means of a measuring probe whose component, which is designed for such measurement, is placed or arrives at a measuring location provided in the wall of the measuring tube.
A method of this type is known from U.S. Pat. No. 4,192,181, granted Mar. 11, 1980, and U.S. Pat. No. 4,230,180, granted Oct. 28, 1980. The measurement of the pressure takes place, for example, for geophysical investigations, e.g. for tunnel construction, for investigations of the underground or subterranean regions at dams or other constructions or also for determining the lowering of the water table.
According to the prior art method, the measurement of the pressure occurs in that a valve provided in the wall of the measuring tube which is opened by the measuring probe, establishes a connection with an inner chamber of the measuring probe in which the measurement takes place. Because of the transition of the medium to be measured into the measuring probe, it is possible for changes of pressure to take place which lead to a faulty result. Furthermore, it is possible that solid particles can lead to malfunction of the valve mechanism used for this purpose.